1. Field of the Invention
The present invention relates generally to integrated circuit package technology and, more particularly, to an increased capacity semiconductor device or package (e.g., a quad flat pack or QFP semiconductor package) which includes a uniquely configured leadframe adapted to provide various efficiencies and economies in the manufacturing process for the semiconductor package.
2. Description of the Related Art
Semiconductor dies are conventionally enclosed in plastic packages that provide protection from hostile environments and enable electrical interconnection between the semiconductor die and an underlying substrate such as a printed circuit board (PCB) or motherboard. The elements of such a package include a metal leadframe, an integrated circuit or semiconductor die, bonding material to attach the semiconductor die to the leadframe, bond wires which electrically connect pads on the semiconductor die to individual leads of the leadframe, and a hard plastic encapsulant material which covers the other components and forms the exterior of the semiconductor package commonly referred to as the package body.
The leadframe is the central supporting structure of such a package, and is typically fabricated by chemically etching or mechanically stamping a metal strip. A portion of the leadframe is internal to the package, i.e., completely surrounded by the plastic encapsulant or package body. Portions of the leads of the leadframe extend externally from the package body or are partially exposed therein for use in electrically connecting the package to another component. In certain semiconductor packages, a portion of the die pad of the leadframe also remains exposed within the package body. Exemplary semiconductor packages or devices employing leadframes include a through-hole mounting dual type inline package (DIP), a surface mounting type quad flat package (QFP), and a small outline package (SOP).
As indicated above, one type of semiconductor package commonly including a leadframe is a quad flat pack (QFP) package. QFP semiconductor packages or devices are particularly advantageous for their smaller size and superior electrical performance. A typical QFP package comprises a thin, generally square package body defining four peripheral sides of substantially equal length. Protruding from each of the four peripheral sides of the package body are a plurality of leads which each have a generally gull-wing configuration. Portions of the leads are internal to the package body, and are electrically connected to respective ones of the pads or terminals of a semiconductor die also encapsulated within the package body. The semiconductor die is itself mounted to a die paddle or die pad of the QFP package leadframe. In certain types of QFP packages referred to as QFP exposed pad packages, one surface of the die pad is exposed within the bottom surface of the package body. When the leadframe is in its original, unsingulated state, both the leads and the die pad are typically attached to a peripheral dambar, with the attachment of the die pad to the dambar often being facilitated by multiple tie bars which protrude from the die pad.
In those leadframes having the above-described structural attributes, a downset is typically formed in each of the tie bars that results in the die pad and at least portions of the leads residing on respective ones of spaced, generally parallel planes. The downsets in the tie bars are typically formed in close proximity to the die pad. The positioning of the die pad relative to the leads attributable to the inclusion of the downsets and the tie bars is often selected to ensure that the semiconductor die mounted to the die pad is fully covered by the encapsulant material which is ultimately applied thereto and hardens into the package body of the semiconductor package. In addition to ensuring that the semiconductor die is completely covered by the encapsulant material, the position of the die pad relative to the leads resulting from the inclusion of the downsets in the tie bars is also selected to ensure that the wire bonds used to facilitate the electrical connection of the semiconductor die to the leads are also fully covered by the encapsulant material applied thereto.
In the manufacturing process for a semiconductor package such as a QFP package including a leadframe having the above-described structural attributes, the leadframe is typically mounted on a heat block for wire bonding. In this stage of the manufacturing process, a recess having a predetermined depth in which the downsets of the tie bars and the die pad are mounted is formed in the heat block. Stated another way, a recess having a predetermined depth is formed in the heat block to allow the die pad of the leadframe to be mounted and seated therein.
However, one of the drawbacks in the design of the above-described leadframes is attributable to the proximity which must normally be maintained between the inner ends or tips of the leads and the peripheral edge of the die pad. In this regard, if the inner ends or tips of the leads are positioned too close to the die pad, such leads are typically not seated in a stable manner in the recess of the heat block, but rather remain unsupported in such recess, thus causing severe bouncing during the wire bonding process and often resulting in poor wire bonding efficiency. Though this particular problem is lessened by positioning the inner ends or tips of the leads further from the die pad, such increased separation necessitates an undesirable increase in the length of those wires used in the wire bonding process to facilitate the electrical connection of the semiconductor die to the leads. The present invention provides a leadframe which is suitable for integration into a semiconductor device or package such as a QFP package and addresses many of the aforementioned shortcomings. Among other things, the leadframe of the present invention is adapted to provide various efficiencies and economies in the manufacturing process for a semiconductor package including the same. These, as well as other features and attributes of the present invention, will be discussed in more detail below.
Common reference numerals are used throughout the drawings and detailed description to indicate like elements.